Patent GB-593782-A (GB)
Title: Improvements in or relating to the production of protein filaments, fibres, yarns and threads
IPC: D01F4/00
Filed: 1945-06-13
Abstract: Protein artificial filaments, fibres, yarns and threads of improved tenacity and elasticity are obtained by extruding an aqueous alkaline solution of a water-insoluble globular protein containing from 10 to 30 per cent by weight of protein and having a pH of at least 9 into an aqueous coagulating bath containing at p  least 0.1 per cent by weight of formaldehyde, from 0.5 to 10 per cent by weight of one or more strong mineral acids and at least 10 per cent by weight of one or more water-soluble inorganic salts, stretching the formed filaments from 25 to 300 per cent in the coagulating bath, further stretching the filaments at least 50 per cent of their maximum draw ratio in a hot concentrated aqueous solution of one or more water-soluble neutral or acid reacting salts of a mineral acid and then treating them with an aqueous formaldehyde hardening solution. Suitable globular proteins are the phosphoproteins, prolamines and vegetable globulins.  Suitable inorganic salts which may be employed in the coagulating bath are the sulphates of sodium, zinc and aluminium.  The temperature of the coagulating bath may range from 20 DEG  to 80 DEG  C.  As they leave the coagulating bath, the filaments are passed around a godet, the speed of which determines the amount of stretch applied to the filaments in the bath.  The lower portion of the godet is immersed in a buffer bath containing, for example, neutral salts, buffering agents and, if desired, formaldehyde wherein excess coagulating bath solution is removed from the filaments.  The secondary stretching bath, the temperature of which should exceed 60 DEG  C., comprises a solution of, for example, sodium chloride, or a sulphate of sodium, aluminium, zinc or ammonium with the addition of, if desired, organic acid salts such as sodium acetate or potassium formate.  Insolubilization of the filaments is preferably effected by treating them without allowing them to contract, first in a bath containing formaldehyde, sodium chloride and sodium acetate and then in a bath containing formaldehyde, sodium chloride and an inorganic salt of aluminium or a heavy metal such as chromium or zinc.  The hardened filaments may be rendered resistant to hot liquors by further treating them with formaldehyde at elevated temperature, with ketene, sodium nitrite or acetic anhydride, and may also be subjected to neutralizing, anti-shrink, softening, oiling and sizing treatments.  The filaments or fibres obtained, in addition to their improved tenacity and elasticity are said to have a skin on their outer surface and to possess a relatively high degree of orientation. In examples, aqueous sodium hydroxide solutions of casein, soya protein and peanut protein are extruded into coagulating baths containing formaldehyde, sulphuric acid, sodium sulphate, aluminium or zinc sulphate, glucose and in one case stearyl trimethyl ammonium bromide at temperatures of 45 DEG  or 30 DEG  C.  The filaments so formed are stretched in the coagulating bath, withdrawn by a godet immersed in a bath containing sodium sulphate, monosodium phosphate and disodium phosphate, stretched in sodium chloride solution at 89 DEG  C. and wound up on a bobbin. The wound filaments are moistened with sodium chloride solution and immersed in a hardening bath containing sodium chloride, aluminium sulphate and formaldehyde which may be preceded by treatment in another hardening bath containing sodium chloride, sodium acetate and formaldehyde.  The filaments are then washed, neutralized, dried and twisted into yarn.